Dysregulated sympathovagal interplay contributes to gastric mucosal injury following subarachnoid hemorrhage

Figures

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  Figure 1. Temporal evolution of gastric mucosal injury following SAH. Representative images: (A–E) Macroscopic overview of the gastric mucosa at 6, 12, 24, 48, and 72 h post-SAH, respectively, showing the progression of hemorrhagic lesions. (F) Gastric mucosa from sham-operated rats at 24 h, showing an intact surface. Quantitative analysis: (G) Erosion index (EI) was significantly reduced at 72 h (n = 10) compared to 48 h (n = 11) post-SAH (p = 0.028). (H) EI was elevated in the 24-h SAH group (n = 7; median = 13.00 [0.00–16.00]) versus the 24-h sham group (n = 11; 2.00 [0.00–6.00]; p = 0.058). Arrowheads indicate representative hemorrhagic lesions. * p < 0.05, ** p < 0.01.

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  Figure 2. SAH induced time-dependent histopathological changes in the gastric mucosa. Representative H&E-stained sections (10 × objective). Scale bars: (A,B) = 200 μm; (C–F) = 100 μm. (A) 6-h SAH group, showing focal mucosal necrosis with marked congestion, hemorrhage, and edema in the adjacent lamina propria. (B) 12-h SAH group, showing necrosis extending through the full mucosal thickness; the adjacent tissue exhibits prominent congestion, hemorrhage, and inflammatory cell infiltration. (C) 24-h SAH group, showing sloughing of most necrotic mucosal tissue. (D) 48-h SAH group, showing erosions/ulcerations at distinct stages: an early stage with mucosal necrosis and partial sloughing (blue arrow) and a later stage with complete sloughing and initiation of repair (green arrow). (E) 72-h SAH group, showing complete sloughing of necrotic tissue with robust cellular proliferation at the base, indicative of ongoing repair. (F) 24-h sham group, showing normal gastric mucosal architecture. Quantitative analysis: (G) The total histopathological score showed no significant difference between SAH and sham-operated groups at 6, 24, or 72 h. (H) The mucosal erosion/ulceration subscore was…

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  Figure 3. Recording sites for gastric vagal and sympathetic electroneurogram. (A) Anterior vagal trunk (subdiaphragmatic). (B) Left greater splanchnic nerve (distal to the adrenal branch). Labels: ▲ Anterior vagal trunk (subdiaphragmatic), ● Greater splanchnic nerve (distal segment), S: Stomach, E: Esophagus, CG: Celiac ganglion, ADR: Adrenal gland, K: Kidney.

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  Figure 4. Time course of SAH-induced vagal activity changes. Representative raw electroneurogram traces (1.5-s segments) recorded from the subdiaphragmatic vagal trunk. (A–E) Recordings from SAH rats at 6, 12, 24, 48, and 72 h post-procedure, respectively. (F–H) Recordings from sham-operated rats at 6, 24, and 72 h post-procedure, respectively. VNA: vagal nerve activity.

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  Figure 5. Quantitative analysis of vagal nerve electroneurogram following SAH. (A–D) In the SAH group, firing frequency (A) and amplitude parameters (B: positive; C: negative; D: peak‑to‑peak) showed increasing trends at 24 and 72 h. The firing frequency (A) was significantly higher at 72 h than at 12 h (n = 9 per group; P = 0.039). (E–H) Compared with sham, SAH showed no significant differences in firing frequency (E), negative amplitude (G), or peak‑to‑peak amplitude (H); however, positive peak amplitude (F) was significantly increased at 72 h (SAH: n = 9; sham: n = 8; P = 0.043). * P < 0.05, ** P < 0.01.

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  Figure 6. Altered sympathetic nerve activity following SAH. Representative raw electroneurogram traces (1.5-s segments) recorded from the left greater splanchnic nerve (distal segment). (A–E) Recordings from SAH rats at 6, 12, 24, 48, and 72 h post-procedure, respectively. (F–H) Recordings from sham-operated rats at 6, 24, and 72 h post-procedure, respectively. SNA: sympathetic nerve activity.

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  Figure 7. Quantitative analysis of sympathetic nerve electroneurogram following SAH. (A–D) In the SAH group, firing frequency (A) and amplitude parameters (B: positive; C: negative; D: peak‑to‑peak) showed increasing trends at 24 and 72 h relative to other time points. (E) At 24 h, firing frequency showed a non‑significant increasing trend in SAH vs. sham (P = 0.088). (F–H) At 72 h, SAH showed significantly greater positive (F; P = 0.038), negative (G; P = 0.047), and peak‑to‑peak (H; P = 0.023) amplitudes than sham (SAH, n = 7; sham, n = 4). * P < 0.05, ** P < 0.01.

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  Figure 8. ACh and NE levels in gastric tissue after SAH. (A) At 24 h, ACh levels were significantly higher in SAH rats than in sham controls (n = 6 per group; P = 0.020) and remained elevated at 72 h (SAH, n = 4; sham, n = 6; P = 0.056). (B) At 24 h, NE levels were also significantly higher in the SAH group than in the sham group (n = 6 per group; P = 0.009). Data are presented as mean ± SEM; *P < 0.05, **P < 0.01.

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  Figure 9. Autonomic neuromodulation attenuated SAH-induced gastric mucosal injury macroscopically. Representative images: (A) SAH-alone, showing extensive hemorrhagic erosions and ulcerations. (B) SAH + vagotomy, showing an intact surface. (C) SAH + atropine, showing a reduction in the number and severity of lesions. (D) SAH + sympathectomy, showing sparse lesions. (E) SAH + phentolamine, showing sparse lesions. (F) SAH + propranolol, with occasional hemorrhagic lesions. Quantitative analysis: (G) The gastric mucosal erosion index (EI) was attenuated by autonomic neuromodulation. Vagotomy resulted in a significant reduction in EI compared to the SAH-alone group (n = 7 per group; p = 0.038). Arrowheads denote representative hemorrhagic lesions. * p < 0.05, ** p < 0.01.

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  Figure 10. Histopathological assessment of gastric mucosal injury following autonomic neuromodulation. (A–F) Representative H&E-stained sections (10 × objective). Scale bars: (A) = 100 μm; (B–F) = 200 μm. (A) SAH-alone group, showing severe injury with deep necrosis (*) and extensive necrotic sloughing. (B) SAH + vagotomy and (C) SAH + atropine groups exhibited markedly attenuated damage, largely confined to focal epithelial sloughing (→). (D) SAH + sympathectomy, (E) SAH + phentolamine, and (F) SAH + propranolol groups displayed an intermediate phenotype, characterized by superficial necrosis (▼) and moderate epithelial sloughing. (G–J) Quantitative analysis of histopathological gastric mucosal lesion scores. (G) Compared to SAH-alone controls (n = 7), both surgical denervations significantly reduced the total histopathological score: vagotomy (n = 7; p = 0.022) and sympathectomy (n = 8; p = 0.003). (H) The erosion/ulceration subscore was lower in both the SAH + vagotomy (p = 0.021) and SAH + sympathectomy (p = 0.016) groups. (I) The mucosal epithelial injury subscore was attenuated by sympathectomy (p = 0.014). (J) The hyperemia/hemorrhage/edema subscore was decreased in both groups…